Reusable fitting for corrugated tubing

ABSTRACT

A fitting for use with corrugated tubing, the fitting comprising: a nut having a passage therethrough for receiving the tubing, the tubing being corrugated tubing having a series of peaks and valleys; a plurality of retainers positioned forward of the nut, the retainers having a sealing surface for placement in a valley of the corrugated tubing; a body having an annular pocket formed circumferentially around the retainers, the body having a body sealing surface, wherein upon sealing, the tubing is compressed between the sealing surface and the body sealing surface; a spring positioned within a cavity in the retainers, the spring driving the retainers into the pocket when the fitting is not sealed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional patentapplication Ser. No. 60/582,904, filed Jun. 25, 2004, the entirecontents of which are incorporated herein by reference.

BACKGROUND

The flexible gas piping (FGP) system, also referred to as corrugatedstainless steel tubing (CSST) and formerly Interior Gas Piping (IGP) wasdeveloped in Japan and first introduced into that market by Osaka Gasand Tokyo Gas Companies during the early 1980's. The system utilizesstainless steel corrugated tubing supplied in rolls or coils with fieldattachable fittings to distribute gas from a central supply point suchas the meter or regulator to the various appliances within a house orbuilding. The technology, which has likened the process of plumbing ahouse for gas to wiring a house for electricity, substantially reducesinstallation time and hence the associated higher cost of labor. Thetechnology was brought to the United States by the Gas ResearchInstitute who saw it as a means of making gas installations morecompetitive; thereby increasing the percentage of new constructionplumbed for gas and increasing the overall consumption of natural gas ona national basis. The technology was enthusiastically endorsed andsupported by major gas utilities who had seen the significant highercost of installed piping as their single greatest obstacle to sellingmore gas. Code acceptance required more time and effort to obtain, butthe product is now recognized by all national model codes and ANSI, theNational Fire Protection Association/National Fuel Gas Code and istested and recognized by the American Gas Association. This product willeventually supplant black-iron pipe which accounts for approximately 80%of all fuel gas piping today, as well as copper tube which, whileenjoying many of the same advantages of FGP, is being banned from thisapplication at an increasing rate.

There have been multiple types of fittings put into the field. Onefitting introduced into the field used a fiber gasket to make the sealand no special tools were needed to assemble this fitting. This fittinghas a higher incidence of leaks than the flared metal to metal sealsused by other manufacturers.

Another fitting introduced into the field used first a specialized toolto flatten the convolutions at the end of the CSST tube where thefitting was to be attached and then a second tool was used to put asingle flare on the tube end. This product is now off the market due tofailures in the tubing caused by work hardening of the stainless steelin the flattening and flaring process.

Another type of fitting was introduced into the field using no specialtools to make a metal to metal seal by folding the convolutions of thetube back on itself creating a double flare. After a limited time in thefield it was realized that this fitting design was inconsistent inmaking a leak tight seal. The remedy to the problem was to design aninsert type flaring tool; this was used for about three years. A secondredesign was conducted, upgrading the insert tool to a socket typeflaring tool.

Other fittings have been introduced by the Assignee of the presentapplication and are discussed in U.S. Pat. Nos. 6,276,728, 6,079,749,5,799,989, the contents of all these patents being incorporated hereinby reference in their entirety. While these fittings are well-suited fortheir intended purposes, improvements may be made in certain aspects ofthese fittings.

SUMMARY

Embodiments of the invention include a fitting for use with corrugatedtubing, the fitting comprising: a nut having a passage therethrough forreceiving the tubing, the tubing being corrugated tubing having a seriesof peaks and valleys; a plurality of retainers positioned forward of thenut, the retainers having a sealing surface for placement in a valley ofthe corrugated tubing; a body having an annular pocket formedcircumferentially around the retainers, the body having a body sealingsurface, wherein upon sealing, the tubing is compressed between thesealing surface and the body sealing surface; a spring positioned withina cavity in the retainers, the spring driving the retainers into thepocket when the fitting is not sealed.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings wherein like elements are numbered alikein the several Figures:

FIG. 1 is a cross-sectional view of an exemplary fitting in anassembled, unsealed state;

FIG. 2 is a cross-sectional view of an exemplary nut;

FIG. 3 is a perspective view of an exemplary retainer;

FIG. 4 is a cross-sectional view of an exemplary body;

FIG. 5 is a plan view of an exemplary spring; and

FIG. 6 is a cross-sectional view of an exemplary fitting in anassembled, sealed state.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional view of a fitting 10 in an embodiment of theinvention. Fitting 10 includes a nut 100, a body 200, retainers 300 andspring 400. FIG. 1 shows fitting 10 in an open, partially assembledposition. The nut 100 and body 200 may be made from metal (e.g., brass)and machined or cast. Tubing 500 may be corrugated stainless steeltubing (CSST) or other corrugated tubing. In FIG. 1, the fitting isassembled, but not sealed.

Tubing 500 is shown positioned in the nut 100 and body 200. Tubing 500is annular corrugated tubing having an exterior surface having peaks andvalleys. Nut 100 includes a groove 102 and seal 104 (e.g., o-ring) at afirst, rearward end to seal against a jacket 502 on tubing 500 asdescribed in U.S. Pat. No. 6,695,353, the entire contents of which areincorporated herein by reference. The O-ring 104 resists entrance offoreign material into the fitting.

Nut 100 includes external threads 106 that engage internal threads 202on body 200. As described in further detail herein, nut 100 includes anut surface 108 at a second, forward end on which retainer surface 308rides when the body 200 and nut 100 are tightened. Similarly, body 200includes a body surface 204 on a second, forward end, on which retainers300 ride when the body 200 and nut 100 are tightened.

Retainers 300 include a cavity 302 positioned at a front face ofretainer 300 for containing spring 400. Retainers 300 include sealingsurface 304 behind cavity 302. As described in further detail herein,corrugated tubing is compressed between sealing surface 304 and bodysealing surface 206. A retainer rear cavity 306 at a first, rearward endof retainer 300, receives a peak of the tubing 500 when the fitting istightened. When disassembled or in a partially assembled state, thespring 400 drives retainers 300 into a pocket 210 formed in body 200circumferentially around the retainers 300. This moves the retainers 300and spring 400 outside of the outer diameter of tubing 500 to allow forassembly and disassembly. The tubing 500 may be freely inserted into orremoved from the nut when the retainers 300 are in pocket 210. Thus, thefitting 10 may be reused.

In the partially assembled state shown in FIG. 1, the body 200 engagesthe nut 100 but threads 106 and 202 are not fully engaged. Retainers 300are pushed into pocket 210 by spring 400. Tubing 500 is inserted intothe fitting until it contacts body sealing surface 206 at the second,forward end of body 200.

FIG. 2 is a cross-sectional view of nut 100. As noted above, the nut 100includes nut surface 108 at a second, forward end of the nut 100. Thenut surface 108 is angled at an oblique angle less then 90 degreesrelative to a longitudinal, central axis of the fitting 10. This angleis mirrored on retainer surface 308 on the first, rearward end ofretainer 300.

FIG. 3 is a perspective view of a retainer 300. The fitting includes aplurality of retainers and may have three or more retainers. Spring 400is received in cavity 302 to be positioned outside the outer diameter ofthe tubing 500 when the fitting is not sealed. In exemplary embodiments,three retainers are used, each spanning 120 degrees of the tubing. Whenthe fitting is sealed, the three retainers abut at their ends, to form acontinuous retainer ring. Sealing surface 304 compresses one or moreconvolutions of tubing 500 against body sealing surface 206 to form ametal-to-metal seal.

FIG. 4 is a cross-sectional view of the body 200. Body 200 includes anannular recess 212 extending towards a first, rearward end of body 200.Recess 212 receives a forward portion of the retainers 300 when thefitting is assembled. Body 200 includes a tapered surface 214 thatserves as a pilot to align the body 200 with tubing 500. The taperedsurface 214 is at an oblique angle with reference to a centerline of thefitting. Tapered surface 204 is also angled relative to body sealingsurface 206, which is shown as perpendicular to the centerline of thebody 200.

FIG. 5 depicts spring 400. Spring 400 is a wire spring coiled to a reststate having a diameter greater than the outer diameter of the tubing500. Tabs 402 on the spring ends are bent inward to prevent spring 400from jamming on the surface of retainers 300. When the fitting 10 isunassembled or partially assembled as shown in FIG. 1, spring 400 forcesthe retainers outward in a radial direction to position retainers 300within pocket 210. Retainers 300 will stay in place in pockets 210 inthe open position even if the fitting is dropped or jarred. As the body200 is tightened to the nut 100, retainers 300 move inward in a radialdirection compressing spring 400. The inward motion of retainers 300 isdriven by angled nut surface 108 and angled body surface 204, both ofwhich form an oblique angle with reference to centerline of the fitting10.

FIG. 6 depicts fitting 10 in a sealed state. As body 200 is tightened onnut 100, the retainers 300 are driven radially inward throughinteraction with surfaces 108 and 204 as the nut 100 moves towards body200. This causes the sealing surface 304 to be placed in a valley behindone or more peaks of corrugated tubing 500. As the nut 100 and body 200are further tightened, retainers 300 enter recess 212. As the nut 100enters body 200, the first convolution of the tubing 500 is compressedbetween sealing surface 304 and body sealing surface 206. This forms ametal-to-metal seal between the body 200 and tubing 500 and between theretainers 300 and the tubing 500. The seal is such that the outerdiameter of the seal is equal to or not substantially greater than theouter diameter of the tubing 500. This allows the tubing to be removedfrom nut 100 when the nut 100 and body 200 are loosened.

Sealing surface 304 is shaped to closely match the corrugation geometryon tubing 500 and requires less force to make up. The resulting sealfrom sealing surface 304 is not a flare and does not extend beyondtubing outer diameter. Sealing surface 304 reduces applied stress to thetubing 500 as compared to conventional flares. Body sealing surface 206is a line seal for greater reliability

If the nut 100 is loosened from the body 200, spring 400 drives theretainers 300 radially outward until the sealing surface 304 clears theouter diameter of the tubing 500. The tubing 500 may then be removed.This allows the fitting 10 to be reused.

A fitting according to exemplary embodiments of the invention providesnumerous advantages. The push-on design (i.e., the fitting can be pushedover tubing 500) does not require disassembly and is reusable. Fitting10 is staked to prevent disassembly and can be made from a wide range ofmaterials.

While preferred embodiments have been shown and described, variousmodifications and substitutions may be made thereto without departingfrom the spirit and scope of the invention. Accordingly, it is to beunderstood that the present invention has been described by way ofillustration and not limitation.

1. A fitting for use with corrugated tubing, the fitting comprising: anut having a passage therethrough for receiving the tubing, the tubingbeing corrugated tubing having a series of peaks and valleys; aplurality of retainers positioned forward of the nut, the retainershaving a sealing surface for placement in a valley of the corrugatedtubing; a body having an annular pocket formed circumferentially aroundthe retainers, the body having a body sealing surface, wherein uponsealing, the tubing is compressed by contact between the retainersealing surfaces and the body sealing surface thereby deforming thetubing to form a seal; a spring positioned within a cavity in theretainers, the spring driving the retainers into the pocket when thefitting is not sealed; wherein the body sealing surface is substantiallyperpendicular to a centerline of the fitting; wherein the nut includes anut surface at a forward end of the nut, the nut surface engaging aretainer surface on the retainers to direct the retainers towards acenterline of the fitting upon engagement of the nut and body; and thebody includes a body surface at a forward end of the body, the bodysurface having an oblique angle with respect to a centerline of thefitting, the body surface engaging the retainer to direct the retainerstowards the centerline of the fitting upon engagement of the nut andbody.
 2. The fitting of claim 1 wherein: the nut surface has an obliqueangle less than 90 degrees with respect to the centerline of thefitting.
 3. The fitting of claim 2 wherein: the oblique angle ismirrored on the retainer surface.
 4. The fitting of claim 1 wherein: theretainers include a rear retainer cavity opposite the sealing surface,the rear retainer cavity receiving a peak of the corrugated tubing. 5.The fitting of claim 1 further comprising: tubing mounted in thefitting; wherein when the fitting is not sealed, the spring and theretainers both have an inner diameter greater than an outer diameter ofthe tubing.
 6. The fitting of claim 1 wherein: the nut includes exteriorthreads that engage threads formed on an interior of the body.
 7. Afitting for use with corrugated tubing, the fitting comprising: a nuthaving a passage therethrough for receiving the tubing, the tubing beingcorrugated tubing having a series of peaks and valleys; a plurality ofretainers positioned forward of the nut, the retainers having a sealingsurface for placement in a valley of the corrugated tubing; a bodyhaving an annular pocket formed circumferentially around the retainers,the body having a body sealing surface, wherein upon sealing, the tubingis compressed by contact between the retainer sealing surfaces and thebody sealing surface thereby deforming the tubing to form a seal; aspring positioned within a cavity in the retainers, the spring drivingthe retainers into the pocket when the fitting is not sealed; whereinthe body sealing surface is substantially perpendicular to a centerlineof the fitting; wherein the body includes a tapered surface at a forwardend of the body, the tapered surface providing a pilot surface to alignthe tubing with the body, the tapered surface extending beyond the bodysealing surface.
 8. A fitting for use with corrugated tubing, thefitting comprising: a nut having a passage therethrough for receivingthe tubing, the tubing being corrugated tubing having a series of peaksand valleys; a plurality of retainers positioned forward of the nut, theretainers having a sealing surface for placement in a valley of thecorrugated tubing; a body having an annular pocket formedcircumferentially around the retainers, the body having a body sealingsurface, wherein upon sealing, the tubing is compressed by contactbetween the retainer sealing surfaces and the body sealing surfacethereby deforming the tubing to form a seal; a spring positioned withina cavity in the retainers, the spring driving the retainers into thepocket when the fitting is not sealed; wherein the body sealing surfaceis substantially perpendicular to a centerline of the fitting; whereinthe nut includes a nut surface at a first, forward end of the nut, thenut surface engaging a retainer surface on each retainer to direct theretainer towards a centerline of the fitting upon engagement of the nutand body; wherein the nut surface has an oblique angle less than 90degrees with respect to the centerline of the fitting; the oblique angleis mirrored on the retainer surface; wherein the retainers include arear retainer cavity opposite the sealing surface, the rear retainercavity receiving a peak of the corrugated tubing; when the fitting isnot sealed, the spring and the retainers both have an inner diametergreater than an outer diameter of the tubing; wherein the body includesa tapered surface at a forward end of the body, the tapered surfaceproviding a pilot surface to align the tubing with the body, the taperedsurface extending beyond the body sealing surface to enter the tubing.